1. Field of the Invention
This invention relates to applying electric fields to various parts of the body for medical treatment. More specifically, this invention applies a changing magnetic field on human tissue, wherein the time change of magnetic field strength (dB/dt) produces a resultant electromotive force (EMF) on the ions in the tissue such as that caused by a direct electric current between two electrodes. Thus, the invention treats human tissues with time changing magnetic fields that induce an electric field.
The invention also lies generally in the field of ion propulsion. More specifically, the invention relates to using a moving magnetic field such as those found in the area of plasma physics with certain applications concerned with rocket propulsion and controlled fusion. The application of this invention is not in these areas but is in a lower energy regime with application for the medicinal treatment of human bone, blood, tissue, and organs by the application of an electric field without the use of electrodes.
2. Description of the Prior Art
DC-like currents are recognized as providing medicinal benefits when applied to biological materials. For example, DC-like currents applied on or beneath the skin's surface have been effective in promoting rapid healing of bones, tissues, and even regrowth of spinal cord axons.
Typical apparatus have relied on electrode-imposed electric fields to impart the electromotive force required to produce the DC-like electric currents in treated tissues. The electrodes are inserted beneath the skin. For example, the use of electrodes to induce currents to treat spinal cord injuries is disclosed in Borgens et al., “Applied Electric Fields in Clinical Cases of Complete Paraplegia in Dogs.” Restorative Neurology and Neuroscience, Vol. 5, pp. 305-322 (1993).
The invasive nature of electrodes threatens the beneficial outcome of the clinical treatment and production of uniform electric fields within the treated tissue. For example, the electrodes can cause infection or become displaced. Moreover, the electric fields produced are non-uniform in both intensity and geometry due to the polarization of the surrounding media at each electrode with oppositely charged ions that weaken and distort the electric field.
The basic concept for the beneficial application of a magnetically generated Lorentz force field to a volume is disclosed in Spiegel (U.S. Pat. No. 5,200,071). In contrast, the invention of the instant application discloses an invention that generates an equivalent electric field with both dynamic and time changing magnetic fields. The invention of the instant application further discloses an invention that generates an equivalent electric field that will stimulate the growth, repair, and renewal of damaged human bone, blood, tissue, and organs. The equivalent electric field also can be used to block specific nerve signals to eliminate pain. The equivalent electric field allows the transdermal transport of efficacious ionic components to specific locations within the tissue. The equivalent electric field can be increased to such power that it will destroy certain volumes of cancerous tissue.
Baermann et al. (U.S. Pat. No. 3,051,988) disclose a magnetic material manipulation device that is superficially similar in appearance to an embodiment of the device disclosed herein. Baermann's device is intended to handle magnetic material for industrial purposes. It uses low rotational velocities and does not generate significant electrical fields. It has no specified medical application and has no mention or understanding of the field generation process disclosed herein.
In a series of patents, Ryaby et al. (U.S. Pat. No. 4,105,017; U.S. Pat. No. 4,266,532; U.S. Pat. No. 4,266,533; and U.S. Pat. No. 4,315,503) disclose a magnetically induced current of specific frequency and amplitude for clinically treating living tissue. The current is induced by an electromagnetic coil. As the coil is electrically energized, it generates a resultant time varying magnetic field. The electric field, and consequent electric current induced by such a coil, must be of a reversing nature. The system disclosed could never produce a DC or rectified AC electric current in treated tissue. Instead, Ryaby et al. produce pulses of induced AC current of specific frequencies and modulations that, although contradicting the teachings of the other references, are purported to be clinically efficacious.
Furthermore, Ryaby et al. teach a medical treatment device that is capable of generating only AC current. The AC current is developed by a time varying single electromagnetic coil that is spatially static. Ryaby et al. in no way suggest the development of electric currents from spatially dynamic magnetic fields. Ryaby et al. do not suggest the generation of electric fields with a stepwise changing magnetic field.
Horl (U.S. Pat. No. 4,727,857) discloses a moving disk with a single set of opposite polarity permanent magnets on one or both faces of the disk. This device produces spatially dynamic magnetic fields that will generate a reversing sinusoidal electric field with each revolution of the disk. Horl teaches to produce only purely sinusoidal electric fields and currents near the surface of each magnetic pole face. Therefore, Horl neither teaches nor suggests to use asymmetrical directed electric currents are an intended resultant clinical benefit. Rather, Horl merely teaches to provide such clinical benefit as may accrue through the action of a pulsing magnetic field of a singular geometry. Such electric fields as generated by this device will be sinusoidal and thus, as shown by cited studies (i.e. Reich and Tarjan) of little therapeutic benefit.
In the article titled “Magnetic Field Therapy to Support Keratotomy,” Ivashina et al. teach to use a moving set of magnets to enhance recovery rates and reduce pain. Ivashina teaches to generate a field that is purely sinusoidal and as a result produces very limited charge transport. Ivashina et al. do not teach or suggest a “square wave” electric field that can produce significant charge transport of the type required by the DC-like current shown to be effective in the Reich & Tarjan study. In addition, Ivashina et al. teach to use simple split fields and not a continuous exposure to a magnetic array. In addition, Ivashina et al. do not teach or suggest incorporating specifically designed permanent or electromagnets that generate dynamic and stepwise changing magnetic fields to induce a continuous and uniform DC-like “square wave” electric field.
Although Abbott et al. (U.S. Pat. No. 5,338,286) do show a magnetic field that increases at a constant rate over 230 μsec and then decreases rapidly over 30 μsec (i.e. FIG. 1), the device taught would be incapable of working at the higher voltages and currents necessary to heal tissue in the same manner that a direct current made between electrodes would.
The issue as to the rejection as being anticipated by Abbott et al. is weather on not someone skilled in the art would be able to extend the inefficient application that Abbott et al. teaches by at least two orders of magnitude to the present teaching.
Furthermore, Abbott et al. focus on producing a rounded saw-tooth shaped magnetic field. Abbott et al. stated the following in col. 2, lines 26-35:                We have discovered that the known biological and therapeutic stimulation by pulsing magnetic fields or by pulsing induced or direct electric fields as practiced with the application of pulses which have heretofore been configured with rapid changes in magnitude or direction of the fields can be improved significantly by modifying the configuration of these pulses to selectively reduce the higher-frequency components of the equivalent spectrum. (Emphasis added by Applicant.)        
Therefore, the object of Abbott et al. is to modify only the leading edge of the longer positive pulse. In addition, Abbott et al. state at col. 4, lines 3-7, the following:                It has been found that the bioresponse of PEMF signals is sharply improved when the rise and fall times in the electric field are lengthened, and, in particular, when the amplitude changes are made less abrupt by rounding the profile of the pulses.”        
While other earlier teachings, i.e. Ryaby etc., focus on the distinction of variable rates of increase and decrease in the magnetic and thus the induced electric fields, the Abbott et al. merely suggest producing “bursts” of asymmetrical signals. None call for continuous repetitive asymmetrical signals without a delay between repetitions. In contrast, Abbott et al. Claim pulse trains of approximately one hundred (˜100) cycles at a frequency of approximately 40 kHz. These 40 kHz bursts are repeated at a frequency of 1.5 Hz or every 0.667 seconds. Thus, during every two-second interval of “treatment”, the sum total time for the three one-hundred cycle bursts would be 0.075 seconds. However, while this percentage may vary slightly within the prior art, it remains representative.
Although Abbott et al. make no direct reference to the actual strength of the induced electric fields in the treated tissue, Abbott et al. cross-reference Ryaby. Ryaby (U.S. Pat. No. 4,105,017) teaches a pattern of pulses similar to that of Abbott et al. Because the direction of the signal (i.e. positive or negative) is arbitrary and subject to sensor orientation, the overall shape of the signal is determinant. As discussed in detail below, there are two portions during each cycle of the induced electric field. Any asymmetric electric field that is generated by a pulsed magnetic coil will have a larger voltage for the faster (shorter in time) part of the cycle and a lower voltage for the longer lasting part of the cycle. Thus, in Ryaby, the “positive” portion of the cycle is similar to the negative portions of Abbott et al.; the same is true of Ryaby's negative going voltage. With regard to the longer lasting part of the cycle, Ryaby claims a maximum of 3.7 mV/cm (0.0037 volts/centimeter) “at the face of the treatment coil” and 1 mV/cm at a distance of ˜3.8 cm “from the face of the treatment coil”.
Abbott et al. and Ryaby teach waveforms that yield a very specific therapeutic effect on bone. The results being claimed by them result from a variety of short pulse trains of electric field at high frequency.
In contrast to Abbott et al. and Ryaby, the medical community as proffered by Reich et al. in The International Journal of Dermatology is that the primary determinative factor in therapeutic benefit of applied electric fields is the effective transport of a minimum quantity of electric charge. That is, there is a measurable therapeutic result only if a specific amount of electric charge is moved in the volume of the wound. Although claims of therapeutic results are made for various adaptations of the existing technology, all creditable claims in the prior art refer to bone treatment with days and weeks of nearly continuous treatment. Because bones have a much higher conductivity than other tissues, it is possible with extended treatment times to produce the required transfer of charge.
The remaining prior art has attempted to treat the above clinical problems with the insertion of electrodes to generate an electric field. The breath and effectiveness of these methods are described in the following publications: “Electric Fields in Vertebrate Repair” and “The Body Electric”. Evidence of the potential application to regeneration of nerve tissue in mammals is most recently given by Borgens et al. in the report, “Applied electric fields . . . in Dogs.” All of these references agree that the most significant beneficial results are obtained through the application of DC currents that mimic the body's own mechanism.
Ryaby (U.S. Pat. No. 4,315,503) rely on physical assumptions that as described are either unclear or incorrect. Furthermore, Abbott et al. encorporate by reference Ryaby. Both patents by Ryaby (U.S. Pat. Nos. 4,315,503 and 4,105,017) teach a circuit as follows:                The signal across the treatment coil decays in a second pulse segment along the portion of the curve designated 40 in FIG. 5a. The slope of that curve is determined by the L/R time constant of the circuit of FIG. 4, i.e., the inductance of the treatment coil and the effective resistance of the circuit, including distributed factors of capacitance, inductance and resistance.        
Clearly there is no teaching of a second circuit with a different value for L/R. In addition, Ryaby states, “In FIG. 5a, the signals at the treatment coil 22 and hence the induced signal within the tissue to be treated are shown.” In general, this is not a true statement. The voltage or “signal” induced within the tissue will not be identical or the “same” as the voltage at the coil. It is established that the induced signal is a function of the time rate of change of the magnetic field within the tissue, dB/dt. The magnetic field is a direct function of the current, i(t), within the coil and as is shown in the current patent:i=i0{1−e−(R/L)t} for the growth of current in the coil, and i=i0e−(R/L)t for the decay of current in the coil.
The exception to this would be for very short times, t, when t>>L/R. Under this exception, the voltage signal imposed on the coil will induce a smaller but similar signal in the tissue.
If the signal being imposed on the coil is repetitive, then:i≈E/2πf if 2πfL>>Rwhere f is the frequency of the cycle, L the inductance of the coil, and R the total resistance in the circuit. Thus, at very high frequencies, the response of the current in the coil is nearly instantaneous with minimal growth and decay times between imposing a voltage on the coil and having full current in the coil.
This assumption is contradicted by Ryaby in claim 1(c) of U.S. Pat. No. 4,105,017 where he claims burst pulse frequencies of between 500 Hz and 100 Hz. At these low frequencies, the lag time of current growth and decay would be very significant and the above assumptions fail.
Therefore, although Ryaby seems on first glance to be dealing with PEMP, the technology is not cable of inducting the therapeutic currents that are similar to a direct current supplied to tissue directly with electrodes. Certain substantial criteria can only be achieved with a higher energy dual circuit of the type taught by the current patent application.
Likewise, Abbott et al. is not capable of inducing sufficient electric fields with sufficient Duty Cycle to create the therapeutic effects that are similar when connecting a direct current directly to tissue using electrodes.
There is no prior art that teaches a method for achieving strong enough induced electric fields of sufficient duration (Duty Cycle) to produce the necessary quantity of charge transport in tissue of low conductivity.
Abbott et al. do not teach a magnetic field with sufficient Duty Cycle or strength to create therapeutic results. Low energy electric signal wave trains of high frequency bursts, such as those taught by Abbott et al. with long intervals between bursts, produce low energy electric treatment fields with low efficiency Duty Cycles. The Duty Cycle taught by Abbott et al. is a pulse train of approximately one hundred (˜100) pulses with a primary signal of two hundred microseconds (200 μs) and an opposite polarity signal of fifty microseconds (50 μs), to be repeated at 1.5 Hz frequency or a period of 0.667 s.
The following formula calculates this Duty Cycle:D.C.=((0.0002*100)/0.667)*100=3%
Thus, the effect of the primary signal is transmitted to the patient for 3% of the time of the treatment. The electric field strength of Abbott et al.'s teaching is not directly disclosed. Abbott et al. state that the coil that produces his induced electric field is powered by a 1 volt regulated DC power supply. Simple analysis of the inductance and driving voltage yields maximum electric treatment field strength of less than fifty 0.5 microvolts per centimeter (<0.5 μV/cm). Voltages in this range will yield nanoamps (0.000000001 A) or less induced in the patient. However, Reich et al. have established that currents in the microamp (0.000001 amps) range are required for effective therapeutic results. If higher induced voltages are achieved, as claimed, they are of such short duration and of such low Duty Cycle efficiencies (3-7%) as to make charge transport negligible.
The teachings of Abbott et al., Ostrow, Rohan, and Ryaby are capable of producing effective electric fields that are two or three orders of magnitude less than the current invention. The methods used by the earlier teachings will not allow for the currents, voltages, or Duty Cycles that are necessary to produce sufficient electric charge transport as defined by Reich et al.
As has been shown above and in the current patent application, such levels of energy transmission and Duty Cycles can only be produced by at least a two order of magnitude enhancement of any of the prior art. Any increase of such magnitude requires a significantly change in the overall design and circuits.
The extension of previous teachings by someone skilled in the art will not resolve the problems of low Duty Cycle or deal with the high volt discharge and high temperature concerns that are created with the significantly higher power of the current invention.
Rohan teaches a symmetric magnetic field waveform. As a result, no net charge transport is produced. Accordingly, no therapeutic effects would result in the treated tissue. Using the model of the current teaching the Duty Cycle for Rohan is 0% since a purely sinusoidal has equal positive and negative going portions and thus will do no work in transport of charges.
Furthermore, the teachings of Rohan et al. do not suggest the invention of the instant application. If we assume, as may be the case in bone, that there is a rectifying effect and only one part of the sine wave is effective and the other half is blocked (half wave rectified). To start with Rohan and then eliminate the delay between pulse trains as is suggested by Rohan at the bottom of the cited paragraph, the Duty Cycle equals 43% using only the “plateau” of the trapezoidal pulse. This is better than 7% of Abbott et al. but less than one half of the 88% of the current teaching. This technology and circuit design would never lead to an effective charge transport system in tissue.
Ostrow does teach a system that is functional description of a delivery system for electrophoresis, if an effective signal that will transport the ions can be generated. Ostrow only teaches a sinusoidal and trapezoidal waveform. As previously shown, such a shape will not have a charge transport capability.
Even a combination of Abbott et al. and Ostrow will yield a minimal benefit. Effective use of Ostrow's teaching will require waveforms of higher power and Duty Cycle.
Abbott et al. refer to Ryaby Pat. No. 4,315,503 as being, “hereby incorporated by reference along with the entirety of said patent.” Since this specific inclusion of description is made the use of that description may be used unless it is specifically delineated against within the Abbot patent. Certain aspects of the Ryaby patents rely on physical assumptions that as described are either unclear or incorrect.
Ryaby, in both U.S. Pat. Nos. 4,315,503 and 4,105,017, describe a circuit having the following features:                “The signal across the treatment coil decays in a second pulse segment along the portion of the curve designated 40 in FIG. 5a. The slope of that curve is determined by the L/R time constant of the circuit of FIG. 4, i.e., the inductance of the treatment coil and the effective resistance of the circuit, including distributed factors of capacitance, inductance and resistance.”        
Clearly there is no teaching of a second circuit with a different value for L/R.